Phys. Rev. B 91, 241201(R) – Published 5 June 2015

We measured the optical conductivity σ̃(ω)spectra of photodoped silicon by optical-pump terahertz-probe spectroscopy and analyzed them with a two-carrier Drude model. Taking into account the values of electron (hole)-phonon scattering rates previously reported in chemically doped silicon, we evaluated the electron-hole scattering ratesγe-h. From 293 to90K, the magnitudes and temperature dependence ofγe-hwere successfully reproduced by a theoretical model including the effects of Rutherford scattering, Coulomb screening, and Pauli exclusion. This suggests that these three factors dominate electron-hole scattering processes in silicon. Below90K, γe-hbecomes larger than that of the theoretical curve, which is attributable to a prolongation of the relaxation time of hot carriers.